1. Field of the Invention
The present invention relates to an oxide semiconductor field effect transistor (hereinafter abbreviated as OS FET) device and a method for manufacturing the same, and more particularly, to an OS FET device and a method for manufacturing the same with a simplified process flow.
2. Description of the Prior Art
To obtain an extremely low off-state current, a channel of the field effect transistor (FET) may be formed using oxide semiconductor (OS) material(s) that has a band gap (greater than or equal to 3.0 eV) wider than Si or Ge. Accordingly, a field effect transistor including a channel layer formed using the oxide semiconductor material(s) is referred to as an OS FET device.
OS FET device has been integrated in thin film transistor liquid crystal displays (TFT-LCD), and now is used in semiconductor industry. However, the channel layer of the OS FET device is sensitive to water, oxygen, acid etchant, or the like. Therefore, any changes in ambient environment in the manufacturing process would alter the characteristics of the OS FET device. Accordingly, there are incessant needs to improve the stability of the OS channel layer and to protect the OS channel layer from environment impacts during manufacturing the OS FET device.